The specific aim of this study is to clarify the relationship between post ischemic brain tissue alkalosis and ischemic neuronal damage, and ultimately to demonstrate that brain alkalosis, as measured by NMR, is a useful marker of neuronal injury. The following Specific Aims are in accord with this goal: 1) To measure brain pH, using in vivo 31P phosphorous NMR spectroscopy serially for one week following the induction of ischemia, and to also measure neuronal damage in the same tissue. These measurements will be performed as a function of the duration of transient forebrain ischemia, as well as for a "protective" hypothermic intervention in the rat. The hypothesis being tested is that the extent of neuronal cell damage is directly correlated with the magnitude, onset time and duration of alkalosis detected from the same tissue. The basis for this correlation is that the temporal profile of alkalosis reflects cellular inflammatory processes, associated with neuronal damage. 2) To measure, at particular time points after ischemia, inflammatory cellular response and glial proliferation, neuronal damage and brain tissue pH, as a function of the duration of transient forebrain ischemia and for a hypothermic intervention. The hypothesis being tested is that inflammatory cellular response and glial proliferation is directly correlated to neuronal damage; hence brain tissue alkalosis is directly correlated to neuronal damage. 3) To measure, in conjunction with the above studies, cerebral blood flow and relative concentrations of brain high energy phosphates and lactates. These measurements will address the relationship between brain tissue alkalosis, and CBF and metabolic changes in the tissue. It is proposed that post ischemic brain pH changes will be closely coupled to ultimate tissue viability, and that the studies will therefore highlight the potential diagnostic significance of chronic pH measurements in stroke patients.